• Energy Research

Natural gas hydrate(NGH) is a clean resource with huge reserves. The depressurization method is an economical and effective exploitation method. In the process of depressurization, reservoir absolute permeability has an important influence on production results. Based on the data of Shenhu hydrate reservoirs, this paper established a depressurization production numerical simulation model. Then, the production performances such as pressure, temperature, gas production rate, cumulative gas production, and hydrate dissociation effect are all studied under different permeability conditions.study the change of reservoir pressure, gas production rate, cumulative gas production, reservoir temperature change and hydrate dissociation effect under different permeability conditions. Results show that higher permeability is conducive to the depressurization of hydrate reservoirs.

Gas production from an offshore hydrate-bearing sediment (HBS) by depressurization will reduce the strength of cementation and increase the effective stress of hydrate reservoirs, which can result ...

Abstract Gas productivity of current hydrate reservoir tests is too lower to meet the demand of the commercial level. The main reasons include the low permeability of hydrate-bearing layer (HBL) and the existence of permeable burdens in natural gas hydrate reservoir, which act as the major barriers for pressure drop propagation during depressurization. However, previous studies are focusing on either permeable burdens or hydraulic fracturing. This paper proposed a novel modified method of depressurization by hydraulic fracturing assisted with sealing burdens. The effects of the radial length and permeability of fractured domain, and the sealing location and length of overburden and underburden layers on hydrate dissociation and gas production were analyzed through numerical simulation. The results indicated:1) The larger permeability and longer radial length of the fracturing domain would promote propagation of pressure drop significantly, and the percentage of gas hydrate dissociation would be increased from 3.99% to 29.86% by hydraulic fracturing. 2) The sealing length of burdens should be larger than the fracturing radial length. The cumulative gas production could be enhanced by 93.25% while the cumulative water production could be decreased by 62.99% compared with no sealing burdens. Base on the novel method, the goals of enhancing gas production and reducing water production would be achieved simultaneously, providing important implications for hydrate commercial exploitation in the future.